The present invention relates to a solid electrolytic capacitor provided with a solid electrolyte layer formed of a conductive polymer, and its manufacturing method.
FIG. 2 shows a cross-sectional view of a prior art solid electrolytic capacitor. It is to be noted that a thickness of each of respective layers in FIG. 1 and FIG. 2 is exaggerated for the purposes of illustration.
In FIG. 2, valve metal 13 provided with a roughened surface layer 14 formed by an etching process is divided into an anode lead out area 12 and a capacitor element area 11 by means of a resist 19 applied onto the roughened surface layer 14.
The capacitor element area 11 is formed on a surface of the roughened surface layer 14 first by depositing dielectric oxide layer 15 by anodization and then a solid electrolyte layer 16, a carbon layer 17 and a silver paint layer 18 in succession. A lead terminal (not shown in FIG. 2) is connected to the anode lead out area 12 and the capacitor element area 11, respectively, thus completing a capacitor element. Then, the entire capacitor element is encapsulated in a packaging resin by resin molding.
It is known that there are a method of electrolytic oxidation polymerization and a method of chemical oxidation polymerization in forming the solid electrolyte layer 16. When the method of electrolytic oxidation polymerization is employed, a manganese dioxide layer is formed in advance on the dielectric oxide layer 15 and the solid electrolyte layer 16 is deposited on the manganese dioxide layer. When the method of chemical oxidation polymerization is employed, the solid electrolyte layer 16 is formed directly on the dielectric oxide layer 15.
With a solid electrolytic capacitor as shown in FIG. 2, valve metal 13 provided with roughened surface layer 14 is divided into an anode lead out area 12 and a capacitor element area 11 by a resist 19. However, solid electrolyte layer 16 is likely to creep to the anode lead out area 12 from the capacitor element area 11 through gaps between the resist 19 and the roughened surface layer 14, often resulting in causing defective insulation or an electrical break-down.
In order to address the problem, such attempts as increasing the pattern width of resist 19, adopting a material having good adhesion to the valve metal 13 and the like have been made. However, it is not easy to obtain good results for many production lots and achieving a low defective insulation rate constantly, and it has been a big problem in view of costs.
The present invention aims to address the foregoing problem and to provide a solid electrolytic capacitor and its manufacturing method, in which the probability of the conductive polymer layer to reach the anode lead out area and cause defective insulation or an electrical breakdown is remarkably reduced. In addition, the present invention provides a solid electrolytic capacitor and its manufacturing method, which do not worsen a good productivity so far enjoyed, while solving the foregoing problem.
A solid electrolytic capacitor of the present invention comprises:
(A) a capacitor element comprising:
a dielectric oxide layer formed on a roughened surface layer on a part of an outer surface of an anode body made of a valve metal;
a solid electrolyte layer formed on the dielectric oxide layer;
a cathode formed of a conductor layer disposed on the solid electrolyte layer, and
an anode lead out area on a remaining part of the outer surface of the anode body;
(B) lead terminals connected to the cathode and the anode lead out area of the capacitor element; and
(C) a packaging resin encapsulating the capacitor element with parts of the respective lead terminals exposed outside.
The solid electrolytic capacitor of the present invention is characterized in having a first separation strip and a second separation strip formed on a part of the roughened surface layer and also having an insulating material applied onto the respective surfaces of the first and second separation strips. According to the present invention, a solid electrolyte layer does not extend to the anode lead out area to cause defective insulation, thereby allowing the probability of an electrical breakdown to be reduced remarkably. Moreover, the present invention does not require the use of special jigs and processes and provides a solid electrolytic capacitor without worsening the productivity so far enjoyed.